Young men who have sex with men (YMSM) experience minority stressors that impact their mental health, substance use, and sexual risk behaviors. Internalized homophobia (IH) and perceived stigma represent two of these minority stressors, and there has been limited research empirically validating measures of these constructs. We validated measures of IH and perceived stigma with a sample of 450 YMSM (mean age=18.9) and a sample of 370 YMSM (mean age=22.9). Results from exploratory and confirmatory factor analyses supported modifications to the IH and perceived stigma scales, ultimately revealing a three factor and one factor structure, respectively. Convergent and discriminant validity were examined utilizing correlations between IH, perceived stigma, and other variables related to minority stress (e.g., victimization). We evaluated predictive validity by examining relations with mental health, substance use, and risky sexual behaviors measured 12-months from baseline. There were mixed findings for IH, with subscales varying in their relations to mental health, drinking, and sexual risk variables. Perceived stigma was not related to mental health or substance use, but was associated with greater prevalence of STIs. Findings supported the use of these modified scales with YMSM and highlight the need for further measurement studies.